1. Field of the Invention
The present invention relates to an information processing apparatus, a recording method and a computer program. More specifically, the invention relates to the information processing apparatus, the recording method and the computer program which record data in a recording medium in unit of file.
2. Description of the Related Art
Nonvolatile semiconductor memories represented by flash memories are being miniaturized and their capacity are being enlarged, and thus they are frequently used for recording high-capacity data such as video data and audio data.
In general, flash memories have reading/writing unit which is called as a page and data deletion unit which is called as deletion block. A size of the deletion block is an integral multiple of a page size. For example, the page size can be 2 Kbytes, and the size of the deletion block can be 32 Kbytes corresponding to 16 times larger than the page size. FIG. 6 is an explanatory diagram illustrating a relationship between the deletion block and the page in the flash memory.
The flash memories should delete data prior to writing of data. When, therefore, data is rewritten in the flash memory, after data is deleted in unit of deletion block, data is written in unit of page. That is to say, a rewriting unit of the flash memories is a deletion block. In most of the flash memories to be used as removal devices, rewriting is enabled in unit of page in a pseudo-manner. In these devices, however, data is internally saved and restored so that the rewriting in unit of page is realized. In general, the rewriting in unit of page causes a reduction in a recording speed because the internal processes such as saving and restore are executed.
In the flash memories, as capacity is made to be higher, a data access is further sped up. A plurality of flash memories in parallel is used inside the device, so that speeding-up of the data access can be realized. For example, when eight flash memories are arranged in parallel, an eightfold access speed can be obtained by simple arithmetic.
On the other hand, when the flash memories in parallel are used, the apparent size of the pages and the size of the deletion block increase. FIG. 7 is an explanatory diagram explaining a case where the flash memories in parallel are used. For example, when eight flash memories, where the size of the page is 2 Kbytes and the size of the deletion block is 32 Kbytes, are arranged in parallel, the apparent sizes of the page and the deletion block become 16 Kbytes and 256 Kbytes respectively which are 8 times as large. When the data access is sped up hereafter, the size of the deletion block also increases according to the speeding-up.
In file systems such as FAT (File Allocation Table), data is allocated to a recording medium in unit of allocation called as cluster including a plurality of sectors. In this case, the size of cluster is set desirably so as to be an integral multiple of the size of the deletion block (at least, the same size) according to characteristics of the flash memories. When the size of the cluster is not an integral multiple of the size of the deletion block, the deletion block is shared by adjacent clusters. In this case, however, when a certain cluster is reused (not in unit of deletion block), rewriting in unit of page is carried out, and a processing speed is lowered.
When the size of the deletion blocks increases according to the speeding-up, therefore, the size of the clusters is desirably increased. In order to obtain the effect of parallelization, data should be accessed in unit of apparent page. When data is accessed in unit smaller than unit of apparent page, the effect of parallelization is not produced.